CN106202704A - A kind of D.C. magnetic biasing impact evaluation method of determining range - Google Patents

Abstract

The present invention relates to a kind of D.C. magnetic biasing impact evaluation method of determining range, for determining the transformer station needing to carry out D.C. magnetic biasing impact evaluation, it is characterised in that described method comprises the following steps: to set up soil model and earthing pole model；Carry out surface potential distribution according to the soil model set up and earthing pole model to calculate；According to the surface potential distribution obtained, determine scope of assessment radius R；According to the scope of assessment R determined, determine the transformer station needing to carry out D.C. magnetic biasing impact evaluation.Compared with prior art, the present invention has and effectively determines and need the transformer station carrying out D.C. magnetic biasing impact evaluation, reduce amount of calculation, reduce modeling complexity and avoid the advantages such as omission.

Description

A kind of D.C. magnetic biasing impact evaluation method of determining range

Technical field

The present invention relates to environmental protection and technical field of direct current power transmission, especially relate to a kind of D.C. magnetic biasing impact evaluation scope Determine method.

Background technology

When DC transmission system is in normal operating condition, system operating mode is bipolar fashion, and DC current is by just The power transmission line at negative the two poles of the earth constitutes loop.But in the case of system debug, overhauling or break down, D.C. high voltage transmission can use The method of operation of one pole ground return circuit.When monopolar ground return runs, earth current field flows through scope environment and can cause relatively electric current Big impact.Due to now, huge DC current flows into the earth through direct current grounding pole, and causes earth potential in a big way Significant change.This earthy change, the AC system for areal may produce impact.Such as, for transformation The AC system of device neutral ground, it will occur that two transformer stations being in different DC potential are constituted back through transmission line of electricity Road, and have DC current to flow to transformer neutral point and Transformer Winding.Make transformator that DC magnetic bias phenomena, transformator occur D.C. magnetic biasing can cause transformer noise to increase, vibration aggravation etc., it is also possible to the overheated and harmonic distortion of AC network occurs Increase.This direct current monopolar operation or run through the earth the impact of AC system is possibly even caused primary equipment when serious Damage or protection malfunction, be in particular cases also possible to the electronic equipment of surrounding is caused a certain degree of interference, long-term Direct current impact is also possible to cause damage to circumferentially burying underground to execute.

After substantial amounts of DC engineering builds up, increasing AC transformer receives D.C. magnetic biasing impact, and everybody is gradually Appreciating the serious of D.C. magnetic biasing impact, therefore D.C. magnetic biasing administers enter as an overall process, the work of normalization Line pipe is managed, and from the design selection of DC engineering, daily monitoring and O&M to earth-current are required for carrying out related work.Therefore, Determine D.C. magnetic biasing coverage, set up corresponding methods of risk assessment, means, be effective guarantee D.C. magnetic biasing management work Means.

DL/T 437-2012 " shape high voltage DC earthing pole fire protection technology " defines direct current grounding pole should carry out when addressing Simulation calculates, and the earth potential that assessment grounding electrode electric current causes raises the impact of the AC transformer on periphery effective grounding, these Affect relevant with transformator location, electric parameter, system wiring and power network wiring etc., so non-clear stipulaties in specification Scope of assessment.

Summary of the invention

It is an object of the invention to for the problems referred to above provide a kind of effectively determine need to carry out D.C. magnetic biasing impact evaluation Transformer station, reduction amount of calculation, minimizing model complexity and avoid the D.C. magnetic biasing impact evaluation method of determining range omitted.

The purpose of the present invention can be achieved through the following technical solutions:

A kind of D.C. magnetic biasing impact evaluation method of determining range, needs to carry out D.C. magnetic biasing impact evaluation for determining Transformer station, it is characterised in that described method comprises the following steps:

1) soil model and earthing pole model are set up；

2) according to step 1) in set up soil model and earthing pole model carry out surface potential distribution calculate；

3) according to step 2) in obtain surface potential distribution, determine scope of assessment radius R；

4) according to step 3) in the scope of assessment radius R that determines, determine the power transformation needing to carry out D.C. magnetic biasing impact evaluation Stand.

The method that the distribution of described surface potential calculates includes that numerical method or software model calculate method.

Concretely comprising the following steps of described numerical method:

21) relation of electric current and the surface potential flowed in soil is determined according to Theory of Electromagnetic Field, it may be assumed that

$\▿\×\stackrel{\→}{E}=0$

$\▿\×\stackrel{\→}{J}=-\frac{\∂{\mathrm{\ρ}}_v}{\∂t}$

$\stackrel{\→}{J}=\mathrm{\σ}\stackrel{\→}{E}$

Wherein, E is electric field intensity, and J is electric current density, ρ_vFor charge density, t is the time, and σ is electrical conductivity；

22) boundary condition that between different electrical conductivity soil, separating surface meets is determined:

V_i=V_j

$\frac{1}{{\mathrm{\ρ}}_i}\frac{{\mathrm{dV}}_i}{dt}=\frac{1}{{\mathrm{\ρ}}_j}\frac{{\mathrm{dV}}_j}{dt}$

Wherein, V_i、V_jFor the current potential of soil boundary, ρ_i、ρ_jFor soil resistivity；

23) determine that reference frame is three Cartesian coordinates, according to step 21) result obtain surface potential meet Partial differential equation:

$\frac{\∂}{\∂x}\left(\mathrm{\σ}\frac{\∂V}{\∂x}\right)+\frac{\∂}{\∂y}\left(\mathrm{\σ}\frac{\∂V}{\∂y}\right)+\frac{\∂}{\∂z}\left(\mathrm{\σ}\frac{\∂V}{\∂z}\right)=f(x,y,z)$

Wherein, V is soil current potential, and (x, y are z) that current source is at (x, y, z) current potential of the contribution at place to f；

24) according to step 22) result determine First Boundary Condition and second kind boundary condition:

First Boundary Condition: v |_s1=v₀

Second kind boundary condition:

Wherein, v₀For border soil current potential, s1, s2 are soil boundary；

25) according to step 23) in equation and step 24) boundary condition, integrating step 1) in set up soil model With earthing pole model, obtain surface potential distribution.

Described step 3) particularly as follows:

31) with the ground connection extremely center of circle, take the minimum radial direction of soil resistivity obtain surface potential distribution second order lead Number；

32) in step 31) in obtain surface potential distribution second dervative in, selected value ε is as the limit of scope of assessment Dividing value；

33) determining value ε position point, calculate distance R between this location point and earthing pole, R is scope of assessment half Footpath.

Described ε is not more than 0.005V/km²。

Described step 4) particularly as follows:

41) judge that the distance between transformer station and earthing pole, whether less than R, is commented if then needing to carry out D.C. magnetic biasing impact Estimate, if otherwise entering step 42)；

42) judge that the distance between transformer station and earthing pole, whether equal to R, affects if being otherwise made without D.C. magnetic biasing Assessment, if then entering step 43)；

43) judge whether the connected transformer station of transformer station meets the transformer station's evaluation condition that is connected, if then needing to carry out directly Stream magnetic bias impact evaluation, if being otherwise made without D.C. magnetic biasing impact evaluation.

Described connected transformer station evaluation condition is: the distance between all connected transformer stations and earthing pole no more than R and Distance between at least one connected transformer station and earthing pole is less than R.

Compared with prior art, the method have the advantages that

(1) the D.C. magnetic biasing impact evaluation method of determining range proposed by the present invention, can be drawn grounding electrode electric current The D.C. magnetic biasing coverage risen has to be assessed in advance.

(2) assess in advance owing to the D.C. magnetic biasing coverage caused has been had, thus when earthing pole addressing, Ke Yixiang To reducing evaluation work, reduce amount of calculation.

(3) the D.C. magnetic biasing impact evaluation method of determining range proposed by the present invention, can determine needs effectively Carry out the transformer station of D.C. magnetic biasing impact evaluation, decrease the complexity of modeling, improve computational efficiency.

(4) when scope of assessment radius being calculated by the present invention, it is only necessary to calculate surface potential and surface potential Second dervative i.e. can determine that, it is not necessary to knows the concrete wiring of electrical network, not only decreases amount of calculation but also reduce the complicated journey of calculating Degree.

(5) except considering in addition to the transformer station in scope of assessment radius in the present invention, it is also contemplated that at scope of assessment The transformer station on radius border, it is to avoid occur omitting, calculate more comprehensive.

Accompanying drawing explanation

Fig. 1 is earthing pole Potential distribution schematic diagram peripherally in the embodiment of the present invention；

Fig. 2 is that in the embodiment of the present invention, earthing pole is distributed along soil resistivity smallest radial direction earth potential second dervative Figure；

Fig. 3 is AC network wiring diagram around earthing pole in the embodiment of the present invention；

Fig. 4 is the method flow diagram of the present invention；

Fig. 5 is the network internal transformer station schematic diagram of the present invention；

Fig. 6 is the network edge transformer station schematic diagram of the present invention.

Detailed description of the invention

The present invention is described in detail with specific embodiment below in conjunction with the accompanying drawings.The present embodiment is with technical solution of the present invention Premised on implement, give detailed embodiment and concrete operating process, but protection scope of the present invention be not limited to Following embodiment.

As shown in Figure 4, the invention provides a kind of D.C. magnetic biasing impact evaluation method of determining range, the method is by meter Calculate the circumferentially Potential distribution that causes of grounding electrode electric current, it is possible to the estimating of D.C. magnetic biasing coverage around the earth polar that achieves a butt joint, Addressing and the D.C. magnetic biasing suppression work of instructing earthing pole are carried out, and the method comprises the following steps:

S1) earthing pole model and soil model are set up, when using numerical computation method to calculate earthing pole inflow DC current, Earthy distribution around, described earth potential calculates and uses following numerical computation method:

According to Theory of Electromagnetic Field, the electric current flowed in soil meets constant current field equation with surface potential, for:

$\▿\×\stackrel{\→}{E}=0---\left(1\right)$

$\▿\×\stackrel{\→}{J}=-\frac{\∂{\mathrm{\ρ}}_v}{\∂t}---\left(2\right)$

$\stackrel{\→}{J}=\mathrm{\σ}\stackrel{\→}{E}---\left(3\right)$

Wherein, E is electric field intensity, and J is electric current density, ρ_vFor charge density, t is the time, and σ is electrical conductivity；

Separating surface between different electrical conductivity soil meets boundary condition and is:

V_i=V_j (4)

$\frac{1}{{\mathrm{\ρ}}_i}\frac{{\mathrm{dV}}_i}{dt}=\frac{1}{{\mathrm{\ρ}}_j}\frac{{\mathrm{dV}}_j}{dt}---\left(5\right)$

Wherein, V_i、V_jFor the current potential of soil boundary, ρ_i、ρ_jFor soil resistivity；

If reference frame is taken as three Cartesian coordinates, then according to the available current potential of formula (1)～formula (3) meet inclined The differential equation is:

$\frac{\∂}{\∂x}\left(\mathrm{\σ}\frac{\∂V}{\∂x}\right)+\frac{\∂}{\∂y}\left(\mathrm{\σ}\frac{\∂V}{\∂y}\right)+\frac{\∂}{\∂z}\left(\mathrm{\σ}\frac{\∂V}{\∂z}\right)=f(x,y,z)---\left(6\right)$

Wherein, V is soil current potential, and (x, y are z) that current source is at (x, y, z) current potential of the contribution at place to f；

This electric current can be regarded as steady current.Although variable-current over time is in flowing, but electric charge is relative Position and density are identical, therefore can compare with electrostatic field.According to uniqueness theorem, define following first boundary bar Part and second kind boundary condition are respectively as follows:

v|_s1=v₀ (7)

$\begin{array}{c}v{|}_{s2}=v_0\\ \frac{\∂v}{\∂n}{|}_{s2}=0\end{array}---\left(8\right)$

Wherein, v₀For border soil current potential, s1, s2 are soil boundary.

May determine that the unique solution of this constant-current field accordingly.According to field equation and boundary condition, can calculate according to practical problem Surface potential is distributed.

Additionally can also use business software model that surface potential is calculated.

S2) with the ground connection extremely center of circle, take the minimum radial direction of soil resistivity (magnetic bias coverage is the widest), obtain ground The derivative of the second dervative of Potential distribution, i.e. every kilometer of epd；

S3) second dervative of earth potential distribution should be a decreasing function, and (suggestion is less than 0.005V/ to take some value ε km², i.e. corresponding bias current change is less than 1A) and as the boundary value of scope of assessment, this point is assessment with the distance of earthing pole Scope radius R；

S4) need to carry out the transformer station of D.C. magnetic biasing impact evaluation in determining scope of assessment:

A. for being in the transformer station of network internal, as it is shown in figure 5, this station from earthing pole distance less than scope of assessment radius R, then should carry out D.C. magnetic biasing impact evaluation.

B. for being in the transformer station of network edge, as shown in Figure 6, when coupled transformer station all at it near ground connection The side of pole, and at least a transformer station is in the scope of assessment that condition a determines, then carrying out D.C. magnetic biasing impact evaluation Time, it is also desirable to the row that this station is accounted for.

As a example by calculating the earth potential scattergram of gained around certain earthing pole shown in Fig. 1, in Fig. 1, X-axis positive direction is soil Earth resistivity minimum direction, zero (0,0) is DC current decanting point, determines around this earthing pole straight according to the following step Stream magnetic bias coverage:

Step 1: use business software CEDGS to set up soil model, calculate earthing pole Potential distribution peripherally；

Step 2: take the minimum radial direction of resistivity (X-axis positive direction), seeks the second dervative that earth potential is distributed, i.e. every public In the derivative of epd, obtain the curve of Fig. 2；

Step 3: taking ε is 0.005V/km², as the boundary value of scope of assessment, in Fig. 2 to should put with earthing pole away from From for 105km, it is scope of assessment radius R；

Step 4: for the transformer station in the range of being less than 105km from earthing pole, be the transformer station of needs assessment；For Transformer station beyond 105km, if meeting method s4) in condition b, then also serve as the transformer station of needs assessment, such as the C in Fig. 3 Stand.

Table 1 shows the AC Substation D.C. magnetic biasing at the scope of assessment edge obtained in the present embodiment according to said method Affecting measured result, with scope of assessment, conclusion determines that condition setting is consistent, demonstrate the accuracy of this method.

Table 1 transformer station distance and neutral point direct current measured result (5000A)

Owing to C station is at earthing pole 117km, at this, the derivative of epd is about 0.0034V/km2, and C stands about You Liangge transformer station is attached thereto (two stations are not the most in the range of 105km), all at close earthing pole side, radial distance about 9km Left and right, therefore its DC current is contributed take and, it is considered to its 2 main transformers, circuit are double loop, then loop resistance is about The half that single line is monotropic, the neutral point current at estimation C station is about 0.0034 × 9 × 9 ÷ 0.25 × 2=2.2A, so separate unit master The neutral point direct current become is about 1.1A, coincide with measured result.If using 105km as assessment border, then C stands not at scope of assessment In, its actual measurement bias current is little, it is not necessary to carry out relevant braking measure.

And A station due to adjacent 500kV transformer station distance about 88km and 78km, then potential difference want big about 60-77 times, Taking intermediate value and be about 68.5 times, in loop resistance, circuit D.C. resistance account for main component, overall loop resistance about 3 times, therefore Bias current is stood compared to C, and neutral point direct current is about 68.5 ÷ 3=22.8 times, adds the bias current tribute to A station of the B station Offering (6.8km, about 0.4 times), the bias current of A station estimation is about about 23 times of C station, about 25A, also kisses with measured current Close.If taking 105km as assessment border, though A stands not in scope of assessment, but model is all being assessed in coupled two 500kV stations In enclosing, it is step s4) middle situation about illustrating b, therefore it is also required to assessment.

Claims (7)

1. a D.C. magnetic biasing impact evaluation method of determining range, for determining the change needing to carry out D.C. magnetic biasing impact evaluation Power station, it is characterised in that described method comprises the following steps:

1) soil model and earthing pole model are set up；

2) according to step 1) in set up soil model and earthing pole model carry out surface potential distribution calculate；

3) according to step 2) in obtain surface potential distribution, determine scope of assessment radius R；

4) according to step 3) in the scope of assessment radius R that determines, determine the transformer station needing to carry out D.C. magnetic biasing impact evaluation.

D.C. magnetic biasing impact evaluation method of determining range the most according to claim 1, it is characterised in that described earth's surface electricity The method that position distribution calculates includes that numerical method or software model calculate method.

D.C. magnetic biasing impact evaluation method of determining range the most according to claim 2, it is characterised in that described numerical value meter Concretely comprising the following steps of algorithm:

21) relation of electric current and the surface potential flowed in soil is determined according to Theory of Electromagnetic Field, it may be assumed that

$\▿\×\stackrel{\→}{E}=0$

$\▿\×\stackrel{\→}{J}=-\frac{\∂{\mathrm{\ρ}}_v}{\∂t}$

$\stackrel{\→}{J}=\mathrm{\σ}\stackrel{\→}{E}$

Wherein, E is electric field intensity, and J is electric current density, ρ_vFor charge density, t is the time, and σ is electrical conductivity；

22) boundary condition that between different electrical conductivity soil, separating surface meets is determined:

V_i=V_j

$\frac{1}{{\mathrm{\ρ}}_i}\frac{{\mathrm{dV}}_i}{dt}=\frac{1}{{\mathrm{\ρ}}_j}\frac{{\mathrm{dV}}_j}{dt}$

Wherein, V_i、V_jFor the current potential of soil boundary, ρ_i、ρ_jFor soil resistivity；

23) determine that reference frame is three Cartesian coordinates, according to step 21) result obtain surface potential meet inclined The differential equation:

$\frac{\∂}{\∂x}\left(\mathrm{\σ}\frac{\∂V}{\∂x}\right)+\frac{\∂}{\∂y}\left(\mathrm{\σ}\frac{\∂V}{\∂y}\right)+\frac{\∂}{\∂z}\left(\mathrm{\σ}\frac{\∂V}{\∂z}\right)=f(x,y,z)$

Wherein, V is soil current potential, and (x, y are z) that current source is at (x, y, z) current potential of the contribution at place to f；

24) according to step 22) result determine First Boundary Condition and second kind boundary condition:

First Boundary Condition: v |_s1=v₀

Second kind boundary condition:

Wherein, v₀For border soil current potential, s1, s2 are soil boundary；

25) according to step 23) in equation and step 24) boundary condition, integrating step 1) in set up soil model and connect Earth polar model, obtains surface potential distribution.

D.C. magnetic biasing impact evaluation method of determining range the most according to claim 1, it is characterised in that described step 3) Particularly as follows:

31) with the ground connection extremely center of circle, take the minimum radial direction of soil resistivity and obtain the second dervative of surface potential distribution；

32) in step 31) in obtain surface potential distribution second dervative in, selected value ε is as the boundary value of scope of assessment；

33) determining value ε position point, calculate distance R between this location point and earthing pole, R is scope of assessment radius.

D.C. magnetic biasing impact evaluation method of determining range the most according to claim 4, it is characterised in that described ε is little In 0.005V/km²。

D.C. magnetic biasing impact evaluation method of determining range the most according to claim 1, it is characterised in that described step 4) Particularly as follows:

41) judge whether the distance between transformer station and earthing pole is less than R, if then needing to carry out D.C. magnetic biasing impact evaluation, If otherwise entering step 42)；

42) judge that the distance between transformer station and earthing pole, whether equal to R, is commented if being otherwise made without D.C. magnetic biasing impact Estimate, if then entering step 43)；

43) judge whether the connected transformer station of transformer station meets the transformer station's evaluation condition that is connected, if it is inclined then to need to carry out direct current Magnetic influence is assessed, if being otherwise made without D.C. magnetic biasing impact evaluation.

D.C. magnetic biasing impact evaluation method of determining range the most according to claim 6, it is characterised in that described connected change Power station evaluation condition is: the distance between all connected transformer stations and earthing pole is no more than R and at least one transformer station that is connected And the distance between earthing pole is less than R.